Brain tumors and intracranial hemorrhages (ICH) have been treated by removing most of the top half of the patient's skull and resecting healthy white matter to get to the tumor or ICH of interest. This approach has the disadvantages of: permanent removal of healthy white matter; increased trauma to the brain via de-pressurization after removal of a large portion of the skull; and long recovery time due to large cranial trauma.
The neurosurgeon can be guided in these procedures using a navigation system that displays the position of surgical tools overlaid on pre-surgical Magnetic Resonance (MR) or Computed Tomography (CT) images in real-time. In these procedures, one or more targets and a surgical path are defined. An ideal surgical path will be determined by the surgeon before the surgery but is not encoded or reflected by the navigation system.
A variety of optical techniques can be used for tissue characterization such surgeries, particularly in the context of identifying a tumour vs identifying healthy tissue. Example techniques include fluorescence techniques (with endogenous or exogenous fluorophores) including time-resolved fluorescence (fluorescence lifetime), broadband spectroscopy, Raman spectroscopy, optical coherence tomography, and numerous others. These techniques vary widely in both their sensitivity and specificity to various diseased states and also in the time and complexity of acquiring a measurement. Fluorescence and broadband spectroscopy for example can acquire an acceptable signal very rapidly (seconds or less), but generally lack specificity to tissue types, while techniques such as Raman spectroscopy require significant time to acquire an acceptable signal (30 s or more) but benefit from enhanced specificity to tissue type. As such, no one technique is ideally suited for intra-surgical analysis.